The research proposed aims to provide a better understanding of how membrane proteins acquire their final structures. The experiments will examine the roles of four sequence elements in establishing the membrane topology of the E. coli serine chemoreceptor. The four sequence elements are the protein's two membrane-spanning segments (tm1 and tm2), a lysine residue adjacent to the C-terminal end of tm2 (lysine-215), and a 13 residue amphipathic sequence situated 8-20 residues C-terminal to tm2. The proposed experiments will identify and analyze the topological consequences of mutations altering the different sequence elements. These studies will help define the primary sequence requirements for the elements to function, and will distinguish between models for how they function. Additional experiments will investigate the manner in which the different sequence elements interact with each other in generating the serine chemoreceptor topology.